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| Title: | Report on the accident to Aerospatiale AS332L Super Puma, G-TIGK, in North Sea 6 nm South West of Brae Alpha Oil Production Platform on 19 January 1995 |
| Micro summary: | This Super Puma successfully ditched in the North Sea following a rotor failure. |
| Event Time: | 1995-01-19 at 1240 |
| File Name: | 1995-01-19-UK.pdf |
| Publishing Agency: | Aircraft Accident Investigation Board (AAIB) |
| Publishing Country: | United Kingdom |
| Report number: | EW/C95/1/1 |
| Pages: | 146 |
| Site of event: | 6 nm south-west of the Brae 'A' oil production |
| Latitude/Longitude: | 58°36'N 01°10'E |
| Departure: | Aberdeen Airport, Dyce, Scotland |
| Destination: | Brae oilfield |
| Airplane Type(s): | Aerospatiale AS332L Super Puma |
| Flight Phase: | Descent |
| Registration(s): | G-TIGK |
| Operator(s): | Bristow Helicopters Limited |
| Type of flight: | Revenue |
| Occupants: | 18 |
| Fatalities: | 0 |
| Serious Injuries: | 0 |
| Minor/Non-Injured: | 18 |
| Other Injuries: | 0 |
| Executive Summary: | The helicopter was conducting a charter flight, ferrying 16 maintenance engineers from Aberdeen to the Brae oilfield. Having just passed a position 120 nm on the 062° radial from the Aberdeen VHF omnirange (VOR) radio beacon, and whilst beginning its descent from 3,000 feet above mean sea level (amsl), the helicopter was struck by lightning. This resulted in severe vibration which, a few minutes later, developed into a loss of tail rotor control, necessitating an immediate ditching in heavy seas. The ditching was executed successfully and the helicopter remained upright enabling the passengers and crew to board a heliraft, from which they were subsequently rescued. There were no injuries sustained and the passengers and crew were later returned to Aberdeen by helicopter and ship. Despite six to seven metre waves and a 30kt southerly wind, the helicopter remained afloat for some three hours and thirty minutes before it was brought alongside a safety vessel. However, whilst secured to this vessel the helicopter's flotation bags punctured and it sank some two hours later, at 1803 hours. The investigation identified the following causal factors: 1. One of the carbon composite tail rotor blades suffered a lightning strike which exceeded its lightning protection provisions, causing significant damage and mass loss. 2. The dynamic response of the gearbox/pylon boom assembly to the tail rotor system imbalance induced rapid cyclic overstressing of the gearbox attachments which was accelerated by the early failure of the upper mounting bolt locking wire, allowing consequent loosening and fatigue failure of this bolt. 3. Complete loss of the yaw control system and a momentary pitch-down as a result of detachment of the tail rotor, gearbox and pitch servo assembly. 4. The lightning strike protection provisions on this design of carbon composite tail rotor blade were inadequate due to it having been developed from an earlier fibreglass blade which had been certificated to lightning test criteria which have since become obsolete. Eight Safety Recommendations have been madeas a result of this investigation. |
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